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Lipid tests.

Q I understand that the treatment of hyperlipoproteinemias falls into one or more of three categories: correction of dietary intake, medication, or surgery. A patient of mine, a 42-year-old white male with coronary artery disease, has changed his life-style in the last year. He stopped smoking, eats a low-fat, well-balanced diet (but consumes three beers daily), and exercises moderately. Despite these modifications, his lab results fluctuate (cholesterol, 244 to 292 mg/dl; triglycerides, 204 to 980 mg/dl). Can you explain this?

A Cholesterol and triglycer-Aide values are subject to analytic and biologic variation as well as variation over time. At this patient's cholesterol level, if the NCEP precision guidelines for cholesterol measurement of [+ or -] 3% CV are met, the maximum analytic error should be about [+ or -] 15 mg/dl from the mean value. Day-to-day biologic variation in an individual ranges from 3.9% to 12.4%.

Medication, acute and subacute illness, secondary disease, and altered metabolic states such as weight loss affect cholesterol levels. Thus the mean analytic plus biologic variabilities could result in a range of values of 176 to 224 mg/dl for an average "true" cholesterol value of 200 mg/dl.[1]

Analytic and biologic variability for triglyceride assay also are present. Alcohol consumption is a major determinant of triglyceride concentration. Since this person is a frequent beer drinker, it is not unexpected for his triglyceride values to be variable. In one study of the analytic and biologic variability of triglycerides, analytic variability had a [+ or -] 4.3% CV while biologic day-to-day variability for individuals had a mean value of [+ or -]25%.[2] At a mean level of 250 mg/dl, one might expect a range of triglyceride values from 125 to 375 mg/dl.

Therapy for atherosclerosis in a young person is multifaceted. Hyperlipidemia is only one of the many important risk factors associated with this disease. Others include heredity, smoking, hypertension, stress, obesity, and illnesses such as diabetes. Changes in lifestyle such as smoking cessation, reduction of dietary fat, weight reduction, and regular exercise are the usual first therapeutic measures undertaken. A variety of medications has been used with varying degrees of success when a change in diet has failed to improve hyperlipidemia. Surgery to improve coronary artery circulation increases the blood supply to the heart muscle but has no effect on the underlying risk factors. A good review of treating hyperlipidemia appears in a JAMA article by Blum and Levy.[3] [1] Belsey, R.E., and Baer, D.M. Cardiac risk classification based on lipid screening. JAMA 263:1250-1252.1990 [2] Hammond. J. Wentz. P; Statland, B.E.; et al. Daily variation of lipids and hormones in the sera of healthy individuals Clin. Chim. Acta 73: 347-352, 1976. [3.] Blum. C.B., and Levy, R.I. Current therapy for hypercholesteroiemia JAMA 261: 3582-3586, 1989.

Daniel M. Baer, M.D., professor of clinical pathology, Oregon Health Science University, and chief of pathology, Veterans Affairs Medical Center, Portland, Ore.
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Title Annotation:Tips on Technology
Author:Baer, Daniel M.
Publication:Medical Laboratory Observer
Date:May 1, 1992
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